The 32-year-old ex-Bayern midfielder was back on the training pitch with the senior squad on Monday, though, with German outlet Sport1 reporting that he had been putting in extra shifts in recent weeks to be prepared for an eventual comeback.

Rummenigge again questioned Mourinho's handling of the situation, saying: "It's difficult to manage a generation change but, nevertheless, you have to do it with tact."

Schweinsteiger, who has previously said United will be his last club in Europe and vowed to be ready for the team if required, wrote on his Twitter account on Monday: "Felt great today! Team is in good shape, results will follow!"

Henrikh Mkhitaryan was also involved in training on Monday, despite a report in the Daily Mail saying the former Borussia Dortmund midfielder had trained alone on Sunday.

The Manchester Evening News has since reported that Mkhitaryan had trained alone out of choice after missing out on a place in the squad for Saturday's 0-0 draw with Burnley and that he hopes to convince Mourinho to bring him back into the side.

Stephan Uersfeld is the Germany correspondent for ESPN FC. Follow him on Twitter @uersfeld.